There isn't an established release date for NetCommunity v5.5 but I think we're getting close! It's an exciting upgrade and probably one of the bigger ones the NetCommunity product has seen. I'm personlly pretty excited about the API changes but this release is going to have lots of other non-API features in it.
Steve MacLaughlin just did a blog post on some of the new items we can expect to see in v5.5. It's a pretty big list and includes some notables like eCards (Michael Sola is happy!), Social Networking, Friendly URLs, Floating CSS Window and many more.
Read Steve's blog for the full list.